1. Field of Invention
Various exemplary embodiments of the present invention relate generally to an electronic device, and more particularly, to a semiconductor memory device and a method for erasing same.
2. Description of Related Art
A semiconductor memory device is a storage device that is realized using a semiconductor made from, for example, silicon (Si), germanium (Ge), gallium arsenide (GaAs) or indium phosphide (InP). Semiconductor memory devices may be classified into volatile memory devices and non-volatile memory devices.
Volatile memory devices are unable to retain stored data when the power is off. Examples of the volatile memory devices may include Static Random Access Memory (SRAM), Dynamic RAM (DRAM) and Synchronous DRAM (SDRAM). Non-volatile memory devices can retain the stored data regardless of power on/off conditions. Examples of the non-volatile memory include Read Only Memory (ROM), Mask ROM (MROM), Programmable ROM (PROM), Erasable Programmable ROM (EPROM), Electrically Erasable and Programmable ROM (EEPROM), flash memory, Phase-change RAM (PRAM), Magnetic RAM (MRAM), Resistive RAM (RRAM) and Ferroelectric RAM (FRAM). Flash memories may be classified into NOR-type memories and NAND-type memories.
Recently, to improve a degree of integration of a semiconductor memory device, research has been conducted on a semiconductor memory device having a three-dimensional array structure. In an erase operation of this semiconductor memory device, a high electric field may be produced between a channel of a memory cell and a word line. When the erase operation is repeated, the memory cell may be gradually degraded due to the high electric field.